A variety of different cementitious materials are used in construction including mortars, slags, grouts, concrete and stucco. Often these construction materials are composed of several different components. To facilitate their use, preferably these materials are ready-mixed, and, even more preferably, ready-to-use. The so-called "ready mixed" cementitious materials are those in which most, if not all, of the dry components are premixed at a manufacturing facility or during transport to a job site. In some instances, ready-mixed cementitious materials may also be mixed with the requisite amount of water to carry out the hydration reaction which results in hardening of the cementitious material. In such instances, the material is also "ready-to-use," i.e., capable of being used without any further additions or mixing.
Although certain cementitious materials, such as cements and mortars for example, are typically delivered ready-to-use, to date a ready-to-use stucco formulation has not been developed. Stucco, or portland cement plaster, is a combination of portland cement-based cementitious material(s) and aggregate (typically sand), mixed with a suitable amount of water to form a plastic mass which will adhere to a surface and harden, preserving any form and texture imposed on it while plastic. As used herein, the term "stucco" refers to portland cement plaster used for coating the exterior surfaces of buildings which falls under ICBOES acceptance criteria AC-11 (Cementitious Exterior Coatings). Stucco is usually applied in one or more coats over metal reinforcement with or without backing. The finish coat is either trowelled, floated, or rough textured. Suitable substrates over which stucco may be applied include, for example, expanded polystyrene (EPS) insulation board, extruded polystyrene insulation foam (XEPS), gypsum sheathing, fiberboard, oriented strand board or plywood, mounted on exterior walls of wood, masonry or steel stud construction. Stucco in the freshly mixed state is a plastic, workable material. It can be applied by hand or machine to conform to any shape.
Stucco is typically applied in three coats. The first coat is called a "base coat" or "scratch coat." This coat is typically about 3/8" thick and is left rough to promote good adherence between it and the second coat, which is generally referred to as the "brown coat." The brown coat is also approximately 3/8 inch thick. The third coat, variously referred to as the "finish coat" or "color coat," is applied over the second coat. Collectively, the three coats are about 3/4 inch thick.
Currently, contractors typically prepare stucco by purchasing bags containing a blend of all the dry ingredients. On site, workers add the necessary water to achieve a mixture with a consistency which is sufficiently fluid so that it can be evenly spread on a wall, while still having enough tackiness that the material adheres to the surface to which it is applied. In some instances, the various components of the stucco composition are purchased individually, mixed on site and then the water added. This approach, however, is inefficient and results in unnecessary labor costs. It would be more efficient to have a ready-to-use stucco prepared at a facility dedicated to preparing stucco.
Another challenge encountered with present stucco compositions and methods are the limitations in controlling the time before the stucco hardens to such an extent that it can no longer be applied. Once water is added to presently available stucco mixes, the stucco must be applied within a limited time period before it dries out and is incapable of being spread. A preferred approach would utilize a trained operator at a central processing facility to add the appropriate additives in order to tailor the period during which the stucco retains sufficient workability in accordance with the time requirements of each job.
Lack of uniformity in stucco preparation at the job site can also be a problem under current methods. Using trained personnel at a central processing facility can significantly reduce this problem.
As noted above, various cementitious materials have been developed which the goal of providing a product having certain improved characteristics. For example, U.S. Pat. No. 5,567,236 describes compositions which can be used to enhance the rheological properties of cement-based materials. However, the additives used to achieve this end are believed to differ from the additives used in the stucco of the present invention.
A variety of patents describe calcium sulfate-based compositions designed to have certain improved characteristics. Examples of such patents include U.S. Pat. Nos. 5,879,446; 5,779,786 and 5,653,797 to Patel or Patel et al.; U.S. Pat. No. 3,869,415 to Williams; U.S. Pat. No. 3,852,083 to Yang; U.S. Pat. No. 3,746,680 to Boricheski; U.S. Pat. No. 3,936,313 to Ericson; U.S. Pat. No. 4,299,790 to Greenberg; U.S. Pat. No. 5,482,551 to Morris et al.; U.S. Pat. No. 5,534,059 to Immordino, Jr.; U.S. Pat. No. 5,718,759 to Stav et al.; and U.S. Pat. No. 4,028,127 to Maske et al. However, the cementitious compositions of the present invention are calcium carbonate and calcium silicate based compositions (approximately 1/3 calcium carbonate and 2/3 calcium silicate) rather than calcium sulfate based compositions. The hydration chemistry, setting process, and mechanical characteristics for these two types of materials is quite different.